FIG. 1 is a block diagram of an exemplary prior art powered system, such as a locomotive 100, for example. In particular, FIG. 1 generally reflects a typical prior art diesel-electric locomotive 100. The locomotive 100 includes a diesel engine 102 driving an alternator/rectifier 104. As is generally understood in the art, the alternator/rectifier 104 provides DC electric power to an inverter 106 which converts the AC electric power to a form suitable for use by a traction motor 108 mounted on a truck below the main engine housing. One common locomotive configuration includes one inverter/traction motor pair per axle. Such a configuration results in three inverters per truck, and six inverters and traction motors per locomotive. FIG. 1 illustrates a single inverter 106 for convenience.
Strictly speaking, an inverter converts DC power to AC power. A rectifier converts AC power to DC power. The term converter is also sometimes used to refer to inverters and rectifiers. The electrical power supplied in this manner may be referred to as prime mover power (or primary electric power) and the alternator/rectifier 104 may be referred to as a source of prime mover power. In a typical AC diesel-electric locomotive application, the AC electric power from the alternator is first rectified (converted to DC). The rectified AC is thereafter inverted (e.g., using power electronics such as IGBTs or thyristors operating as pulse width modulators) to provide a suitable form of AC power for the respective traction motor 108.
As is understood in the art, the traction motors 108 provide the tractive power to move the locomotive 100 and any other vehicles, such as load vehicles, attached to the locomotive 100. Such traction motors 108 may be AC or DC electric motors. When using DC traction motors, the output of the alternator is typically rectified to provide appropriate DC power. When using AC traction motors, the alternator output is typically rectified to DC and thereafter inverted to three-phase AC before being supplied to the traction motors 108.
The traction motors 108 also provide a braking force for controlling speed or for slowing the locomotive 100. This is commonly referred to as dynamic braking, the mechanism or process of which is generally understood in the art. Simply stated, however, when a traction motor is not needed to provide motivating force, it can be reconfigured (via power switching devices) so that the motor operates as a generator. So configured, the traction motor generates electric energy which has the effect of slowing the locomotive. In prior art locomotives, such as the locomotive illustrated in FIG. 1, the energy generated in the dynamic braking mode is typically transferred to resistance grids 110 mounted on the locomotive housing. Thus, the dynamic braking energy is converted to heat and dissipated from the system.
Conventional trains, including one or more locomotives and rail cars, typically include multiple types of braking systems. For example, such trains may include a train line braking system which utilizes an air pipe that is connected to braking systems on each locomotive and each rail car. The locomotive(s) within such trains may also feature independent activation of locomotive air brakes, in addition to hand operated parking brakes and locomotive dynamic brakes. Although locomotive dynamic braking systems are the most recently developed, none of these systems are entirely failsafe in application.
The various types of locomotive braking systems typically vary in their braking performance. For example, dynamic braking systems typically have a faster response time than the train line braking system, which requires additional time to activate and release due to air flow constraints reaching the length of the train. Thus, dynamic braking systems are generally preferred to the alternative braking systems.
Positive train control enforcement systems monitor a train's location and speed relative to its movement authority. If a train is predicted to overspeed or pass a required stop point, the positive train control system activates a penalty brake application to stop the train. Typical contemporary positive train control enforcement systems rely on the train line air brake system to apply the penalty braking. However, use of other braking systems may provide more advantageous benefits within a positive train control enforcement system. This in turn can improve railway capacity, and avert unnecessary penalty applications for aggressive drivers.
Accordingly, there is a need in the industry to maintain the availability and effectiveness of the dynamic braking system, to maintain the practical advantages of using the dynamic braking system. Unfortunately, conventional systems do not provide information regarding the operation and condition of the dynamic braking system in order to ascertain the performance capability of the dynamic braking system. Thus, it would be advantageous to provide a system which can determine this information and further determine the performance capability of the dynamic braking system.